In the process of chemical production plant maintenance, operators should fully carry out risk identification and safety evaluation. If the preventive measures are not in place, it is likely to lead to some mistakes in the work, resulting in accidents. The relevant data show that, in the accidents occurred in the production and maintenance of chemical enterprises, the accidents caused by unsafe behaviors of operators account for about 88% of the total accidents, 10% of the total accidents caused by unsafe conditions in the work, and the other 2% are caused by comprehensive factors. It can be seen that under the same working conditions, the unsafe behavior of the operators is the main cause of the accident.

Ⅰ、 Classification of production equipment maintenance

The maintenance of petrochemical plant and equipment is divided into planned maintenance and unplanned maintenance. Scheduled maintenance is called scheduled maintenance. According to different contents, periods and requirements of planned maintenance, planned maintenance can be divided into minor maintenance, medium maintenance and major maintenance. At present, most petrochemical production units are scheduled to be overhauled once a year. With the application of new materials, new process, new technology and new equipment, the improvement of maintenance quality and the development of prediction technology, some petrochemical production units have been overhauled once every two years.

In the process of production, equipment failure or accident occurs suddenly, and maintenance without or temporary shutdown is called unplanned maintenance. This kind of maintenance is difficult to predict in advance and cannot be scheduled. Therefore, in the current petrochemical production, this kind of maintenance is still inevitable.

Ⅱ、Features of production unit maintenance

Generally speaking, the maintenance of petrochemical plant has the characteristics of complexity and great danger. The complexity is shown in the following aspects: due to the large number of maintenance items, complex maintenance contents, large construction work, concentrated tasks, short maintenance time, large number of personnel, frequent changes in operation form and number of operators. In order to rush in time, overtime is often added, and petrochemical equipment is of various types, structure and performance are different, and the vertical and downward cross operation of various types of work on tower, tower and lower tower, inside and outside the container is conducted, The maintenance is also limited by the environment and climate conditions, all of which add complexity to the maintenance of the device, which is prone to personal injury accidents. On the other hand, the risk of petrochemical production determines the risk of petrochemical overhaul. Because of the inflammable, explosive and toxic substances in the equipment and pipelines of petrochemical plant, the maintenance of the device can not be separated from the hot work, earth moving, and the operation of the tank tower. In objective, there are fire, explosion and poisoning accidents, and serious accidents are prone to occur if the accident is not handled properly.

Practice has proved that accidents are most likely to occur in the process of shutdown, overhaul and start-up of the plant. According to statistics, among the major accidents in Sinopec system, the accidents occurred in the process of overhaul account for 42.63% of the total accidents. For example, during the shutdown and maintenance of a catalytic cracking unit in a refinery, the operator unloaded the flange of the dn800m large oil and gas pipeline with a work order and put it into the blind plate for alignment. Because only the crude purging of the fractionator was carried out before turning over blind-201, the residual combustible gas entered the large oil and gas pipeline and mixed with air for deflagration and fire. When the operator dodged, two people fell from the 6m high platform and one died, One was injured at the waist and the other five were burned.

During the maintenance of a platinum reforming unit in a plant, a worker went down to the tank without gas analysis to see if there was any gas. Because nitrogen was replaced in the tank during shutdown, and there was still nitrogen in the tank, which immediately caused suffocation and fainting. After the accident, due to the lack of anti-virus knowledge, three people went down for rescue and fell down one after another, resulting in two deaths.

During the overhaul of atmospheric and vacuum distillation unit in a factory, the work has entered the final stage. There are 13 manhole in the vacuum tower, of which 8-13 floors have been sealed the first day, and another 15 people continue to seal the manhole on the same day. Just when the three manhole on the first, second and third floors were sealed, an electric welder was working on the extraction line at the bottom of the vacuum tower. Suddenly, an explosion occurred in the tower. A wave of gas rushed out from the manhole on the fourth, fifth and sixth floors. Two workers were thrown to the top of the heating furnace more than 20 meters away and died. Another seven workers were injured and damaged the 14 floor tower tray. The start of the plant was delayed for 10 days. The main cause of the accident was that a valve of the emergency vent line of the vacuum furnace was not equipped with blind plate, and the explosive gas flowed into the vacuum tower from the emergency vent tank along the vent pipe after passing through the furnace pipe.

Ⅲ、Operation risk and safety measures of chemical production plant

The following will introduce the risks and corresponding safety measures of six typical maintenance operations in the chemical production unit area.

1、Corrosive medium maintenance operation

Operational risk

The leaked corrosive liquid and gas medium may cause different degrees of damage to operators' limbs, clothing and tools, and cause environmental pollution.

2、Safety measures

(1) Before maintenance work, the process personnel must be contacted to drain, heat and wash corrosive liquid and gas medium, and the work permit shall be obtained after the analysis is qualified.

(2) Operators shall wear labor protection appliances as required and be familiar with the work contents, especially the opinions signed by relevant departments.

(3) For maintenance in low-lying area, there shall be no accumulated corrosive liquid in the site, so as to prevent slipping and injuring people during operation.

(4) The working surface of corrosive liquid should be lower than the legs, otherwise, the relevant personnel should be contacted to set up scaffolds to prevent the body and clothes from being injured by the residual liquid, but it is not allowed to temporarily support with iron barrels.

(5) When working, wear rubber gloves, protective mask, rubber shoes and other special labor protection articles according to the specific situation.

(6) During disassembly, the joint surface can be washed with clean water to reduce the corrosive effect of corrosive liquid and gas medium.

(7) The limbs, clothes and tools in contact with corrosive medium should be cleaned in time; If there is discomfort, it should be treated in time.

(8) After the completion of the operation, clean the materials and clean the site, and do a good job in cleaning the site.

2、Maintenance of rotating equipment (including valves and motors)

1 、Operation risk

When rotating equipment is overhauled, misoperation of electric and steam sources will cause misrotation, which will endanger the life and property safety of maintenance workers; When the equipment (or spare parts) is large (heavy), improper safety measures may cause mechanical injury.

2、Safety measures

(1) Before maintenance work, the process personnel must be contacted to effectively isolate the system, and the inflammable, explosive, toxic and harmful media in the hot work maintenance equipment and pipelines must be drained, washed and replaced. After reasonable analysis, the work permit shall be obtained.

(2) When repairing live (steam) equipment, contact with relevant personnel and teams, cut off the power (steam) source, and hang the sign of "no switching on, someone working" on the switch box.

(3) The person in charge of the operation project shall implement various safety measures for the operation and handle the work permit and approval; For the extremely dangerous operation, the safety assessment shall be conducted together with the person in charge of safety in the operation area, and the safe operation scheme shall be formulated.

(4) Operators shall wear labor protection appliances as required; Be familiar with the work contents, especially the opinions signed by relevant departments, and implement them carefully before and during the operation.

(5) The disassembled parts and components should be placed in different areas and protected well. The important parts or components should be guarded by special personnel.

(6) When using pneumatic, electric, hydraulic and other tools, it is necessary to operate according to the "safe operation manual" to ensure safe construction.

(7) When the equipment (or spare parts) is large (heavy) and needs multi types of work cooperation, it must be under unified command and prohibited.

(8) The management of oil products should be strengthened, and all waste oil should be poured into the recycling bucket.

(9) After the completion of the operation, clean the materials and clean the site, and do a good job in cleaning the site.

3、High altitude maintenance

1、Operational risk

The working position is higher than the normal working position, which is prone to fall of people and objects, resulting in accidents.

2、Safety measures

(1) The person in charge of the operation project shall arrange to apply for the "work permit" and "permit for work at height", which shall be approved according to the work height; The person in charge of the production department where the operation is located shall sign the opinions of the Department.

(2) The person in charge of the operation project shall check and confirm whether the scaffold (ladder, hanging basket), safety belt, rope and other tools used for high-altitude operation are safe, and arrange the supervisor of the operation site; Warning line shall be set when necessary.

(3) Operators shall wear labor protection appliances as required and be familiar with the work contents, especially the opinions signed by relevant departments; When using the safety belt, it shall be carried out in accordance with the regulations on the use and management of the safety belt; When working with ladders, it shall be carried out in accordance with the regulations on safety management of ladders; When using scaffolds, it shall be carried out in accordance with the regulations on safety management of scaffold use; When working in the basket or hanger, refer to the regulations on safety management of lifting equipment.

(4) When working at height, it is not allowed to work vertically up and down at the same time. When vertical operation is necessary under special circumstances, it shall be approved by the leader of the unit, and special protective shed shall be set or other isolation measures shall be taken.

(5) Avoid working at height at night. When it is necessary to work at height at night, it shall be approved by relevant departments. The person in charge of the operation shall carry out risk assessment, formulate safety measures and ensure sufficient lighting.

(6) In case of severe weather such as gale above level 6, lightning, rainstorm, fog, etc., which affects vision and hearing, or there is no guarantee for personal safety, it is not allowed to work at height.

(7) In the process of work at height, the safety guardian shall often contact with the workers working at height, and shall not engage in other work, let alone leave without permission; When the production system?? In case of any abnormal situation, immediately inform the operators at height to stop the operation and evacuate from the site; In case of major changes in working conditions or working environment, the permit for work at height must be renewed.

(8) After the completion of the operation, clean the materials and clean the site, and do a good job in cleaning the site.

4、Hot work maintenance

1、Operational risk

Heating, slag scattering and spark splashing may cause personnel scalding, fire and explosion accidents, arc radiation, electric shock, etc., which may also cause harm to human body.

2、Safety measures

(1) Before maintenance, contact the process personnel to effectively isolate the system, and clean, flush and replace the inflammable and explosive media in the hot work equipment and pipelines.

(2) After the analysis is qualified, the work permit and hot work permit shall be approved by classification; After the sampling analysis is qualified, no one shall change the process state; During hot work, if the interruption is more than half an hour, sampling and analysis must be conducted again.

(3) The hot work permit shall be carried by the hot work personnel. All operators must be clear about the work contents, especially the opinions signed by relevant departments.

(4) Operators must wear labor protection articles and hold corresponding qualification certificates as required; Before welding and cutting, combustible materials must be removed, warning lines shall be set, obvious signs shall be hung, and the hot work scope shall not be expanded without authorization.

(5) The hot work shall be provided with a guardian and fire extinguisher; During operation, irrelevant personnel are forbidden to enter the hot work site. For moving operation in class a fire forbidden area, the project leader shall inform professional fire protection personnel to assist in supervision on site in advance according to the regulations.

(6) During welding, check the integrity of joints and lines to prevent accidents caused by leakage.

(7) During gas welding, the distance between oxygen cylinder and acetylene cylinder shall be kept at least 5m, the distance between 2 gas cylinder and hot work point shall be more than 10m, and the air pipe shall be checked to be in good condition.

(8) When welding and cutting at heights, fire receiving basin shall be set to prevent sparks from splashing; At the same time, all combustible materials below shall be removed, and trenches, anion wells, cables, etc. shall be covered.

(9) When the combustible gas is under pressure and does not replace the hot work, it is necessary to have the operation plan and implement the safety measures. At the same time, the pressure in the equipment shall not be less than 0.98kpa and 1.5691mpa, so as to ensure that no negative pressure will be formed; The oxygen content in the equipment shall not exceed 0.5%. Otherwise, hot work is not allowed.

(10) When the operators leave the hot work site, they shall cut off the power supply used in construction and extinguish the remaining fire sources in time without any hidden danger.

(11) After the operation, clean the site after the work and do the cleaning and sanitation work on the site.

5、Maintenance work in confined space

1、Operational risk

There are hidden dangers such as hypoxia, high temperature, toxic and harmful, flammable and explosive gases in the confined space, and the safety measures are not in place, which are prone to combustion and explosion, and can cause casualties and other accidents.

2、Safety measures

(1) Contact the process personnel to cut off the power supply connected with the outside world on the equipment, take locking measures and hang warning signs; Effectively isolate all equipment and pipelines connected with limited space or container.

(2) After the confined space is discharged, isolated (blinded), cleaned, replaced and ventilated, and the sampling analysis is qualified, the operators shall apply for the "work permit" and "work permit for entering the confined space" for hierarchical approval. No one is allowed to change the process state after the sampling analysis is qualified.

(3) Before operation, prepare emergency rescue materials, including safety belt, safety rope, long tube mask, safety voltage lighting not exceeding 24 V, anti electric shock (leakage) protector and communication tools.

(4) The guardians should wear labor protection appliances as required and choose the position of safety guardians; In the process of monitoring, it is necessary to keep in touch frequently. In case of any abnormality, the operator shall be informed immediately to stop the operation and evacuate from the dangerous area; At the same time, we must pay attention to self-protection.

(5) Operators shall wear labor protection appliances as required. When entering a confined space for the first time, you must wear a gas mask (long tube or air respirator), and wear a safety belt and safety rope; Be familiar with the work content, especially the opinions signed by relevant departments; The shift system shall be implemented for the workers working in confined space, and the shift shall be changed on time, and the workers shall be withdrawn to rest outside in time.

(6) After the cover plate is removed from the confined space, roadblocks, fences, lights, etc. must be set up to avoid accidents.

(7) When entering the confined space for operation, online analysis must be carried out. In case of any abnormality, timely evacuation shall be carried out.

(8) After the completion of the operation, clean the materials and clean the site, and do a good job in cleaning the site.

6、Electrical maintenance

1、Operational risk

Electric shock hazard, arc hazard or spark accident caused by short circuit may occur during electrical maintenance, which may cause injury to human body such as electric shock, burn caused by arc, explosion and impact injury caused by arc. In addition, electrical accidents may also lead to fire, explosion and power failure.

2、Safety measures

(1) Before maintenance, contact the operator to cut off the power supply connected to the equipment, and take locking measures. Hang the signboard of "no closing and working" on the switch box or main gate.

(2) All work on or near live equipment shall be subject to work permit and the permit management procedure shall be implemented.

(3) Operators shall wear labor protection equipment (in accordance with the requirements of personal protective equipment for substation work) as required, and be familiar with the work contents, especially the opinions signed by operators.

(4) Electrical work can only be completed by qualified personnel with certificate. More than 2 people must be in charge of operation, one of whom shall be supervised.

(5) The electrical monitoring personnel must be trained professionally, obtain the qualification certificate, be qualified to cut off the power supply of the equipment and start the alarm signal; Prevent irrelevant personnel from entering dangerous areas during operation; No other work tasks shall be carried out.

(6) In the maintenance and troubleshooting, no one can change or adjust the setting value of protection and automatic device without authorization.

(7) For the equipment with energy greater than 5.016j/m2, the analysis and prevention of arc hazard must be carried out to ensure safe and effective operation.

(8) For the process or system which is prone to generate static electricity in maintenance, static hazard analysis shall be carried out and corresponding measures and procedures shall be formulated to prevent electrostatic hazards.

(9) Metal ladders, chairs, benches, etc. cannot be used in electrical operation.

Summary

It can be seen that it is necessary to do a good job in the safety work during the shutdown, overhaul and start-up of the device, learn the relevant safety knowledge in the overhaul, understand the dangerous factors existing in the overhaul process, seriously take various safety measures, prevent various accidents, and protect the safety and health of employees.